I think it's really sad how alone Sydney is right now, but with everything else that's going on on the show (the CIA missions plus the mystery of the missing two years), they really don't have time to show a lot of Syd's downtime, when she's just hanging out at home. And her scenes with Jack usually take place at work,so that takes care of that. It's too bad she only had 2 close friends to begin with; now that they're both gone, there's really nobody left.
That's one of the reasons why I'm impatient for her to get back together with Vaughn; so that we'll have at least a few scenes that are happy and normal. I know Sydney's strong, but sometimes it verges on the unbelievable that she's still a normal, functioning human being with everything that's happened to her. I guess that's one of the things we're supposed to accept without looking too deeply into it.